The reemergence of the extracapsular method of cataract extraction in recent years has signaled a major change in cataract surgery. With this technique, the posterior lens capsule is left in situ to stablize intraocular lenses and to serve as a barrier between the anterior and posterior segments of the eye. The major complication of this procedure is late opacification of the posterior capsule, a process which occurs in 35-50% of patients, the majority requiring surgical reintervention. Since no tissue is removed in the surgical incision of an opacified posterior capsule, and since few eyes come to post-mortem histologic examination, little is known of the morphologic features of this complication. Additionally, there have been no experimental studies of central capsular opacification, and no suitable animal model exists. I propose to study the morphologic features of posterior capsular opacification in the cat. Extracapsular cataract extractions will be performed on cats and animals will be sacrificed at sequential times, (0 hours, 1 day, 4 days, 1 week, 2 weeks, 4 weeks, 3 months and 6 months). The development of capsular opacification will be studied by correlating clinical findings with light microscopy, transmission electron microscopy, and scanning electron microscopy. The findings in the cat model will be compared with a more limited study of extracapsular cataract extraction in the primate and in human cadaver (eye bank) eyes to determine if the cat is an appropriate animal model for further investigation of this surgical complication. Improved understanding of the pathogenesis of late capsular opacification will provide the basis for appropriate utilization of an animal model and tissue culture methods in the search for chemical, mechanical, or surgical methods of preventing the occurence of this complication.